A curious phenomenon over the years has changed to some degree the freedom with which participants in the Middle Kingdom can identify their self-chosen roles without reference to a kingdom award of some kind or a relationship with senior armored combatants. I'm not saying it's a bad thing, exactly, just an interesting thing.
The terms I have in mind are sergeant, captain, company and man-at-arms.
When I joined the SCA in 1982, none of these were official designators. That is, they didn't describe roles that the kingdom as an official body took an interest in, nor was there any custom associated with them.
Sergeant was understood at the time to designate any sort of sub-commander in the melee field. The leader of a group of fighters might choose to call himself a captain, or be referred to as such. A company was little-used at the time, but over the years came to refer to a group of any kind, but usually an armored combat unit that modelled itself on late medieval lines. Man-at-arms was used in the period sense: any armored combatant who wore full harness of the sort that knights of his period wore was by definition a man-at-arms, even if he was in fact a knight or a squire.
Of course, no one went around calling themself Sergeant Blank, but it was useful to be able to say "that's Lord Blank. He makes a good sergeant." It was easy to designate the leader of your unit (perhaps a company) as a captain, and sometimes even call them Captain Blank. And if one wasn't a knight or squire, man-at-arms was a good, dignified description that was more satisfying than "fighter."
This began to change in the early 1990s when the kingdom introduced the Order of the Red Company and chose to designate the members as Sergeants. Naturally, the very people one thought of as sergeants in melee combat were the first to be put in this order, but it removed the descriptor as a general term. If one wasn't a member of the Red Company, it was no longer convenient to say "I'm usually a sergeant." This was probably the easiest of these changes to swallow, because in the Middle Ages, there really were Sergeants-at-Arms who were officials of the crown.
Later, the kingdom added the Order of the Gold Mace (ironically, sergeants traditionally bore maces), and these were sergeants who were promoted out of the Red Company Order to be Captains. This effectively made these two orders, together with the chivalry, the official officer structure of the Middle Kingdom's army. It was clever, but it took away another private means of describing roles. You can't readily call yourself "Captain Blank", without having people perhaps assume that you are claiming to be a member of a kingdom order.
Obviously, both these orders and the not-yet-mentioned Order of the Greenwood Company have made calling one's melee unit a company a slightly more sensitive matter. It's still ok to do this, and less problematic than using the terms sergeant or captain, but one may occasionally have to explain to some people that no, you're not calling your group an order, you're just using a period descriptor.
Finally, a recent innovation, and this is more custom than an official change, is to use the term man-at-arms not generally to designate all those not a knight, squire, sergeant or captain, but instead more specifically to describe only those in that category who are students of a senior fighter, not necessarily a knight. So a man-at-arms is not a person of substance who wears expensive harness and is experienced and competent, but instead another kind of dependant. One can no longer say to a question regarding fighting rank "I am a man-at-arms" if one lacked a specific role or title and yet was a person of some consequence. The rejoinder would now be "Oh? Whose?" And then one would have to explain no, you mean it as a general term, which might puzzle the questioner, who isn't likely to understand anymore without further explanation.
I'm not complaining, exactly. I just find it a trifle inconvenient. Stormvale, without any resident knights or captains or active squires or sergeants, nevertheless has at least half-a-dozen experienced combatants who don't have an easy period designator, because we are half a step outside the regular kingdom structure. Nor can we call our leader of the moment a captain without potentially ruffling feathers. The real answer is to get more integrated into the kingdom and regional fighting community and grow our own conventional relationships, of course.
What does it all mean? Well, the SCA has always been a rather hierarchical community, and the Middle Kingdom is not behindhand in that phenomenon. As the years go by, perhaps it is inevitable that more structure should be imposed or agreed upon. There was very little structure in the fighting community when I joined. Knights were rare, god-like creatures, and there weren't enough of them to go around as teachers, leaders and examples. That made being a squire practically a junior knight, as squires were also necessarily rather rare. The changes since then are clearly a species of improvement, and are also closely tied to the kingdom's desire to foster a more competitive army at Pennsic, since we've been having trouble competing with an East Kingdom that had become more militarily adept for quite a while there.
And that's a topic for another post.